Summary of Significant Accounting Policies - Restricted Cash and Accounts Receivable (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Restricted cash
Restricted cash	$ 0	$ 958
Accounts Receivable [Abstract]
Allowance for doubtful accounts receivable	3,000	2,600
Retainage	37,963	$ 42,547
Retainage, long-term	$ 6,000

Amount of allowance for credit loss on accounts receivable.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Balance Type:	credit
Period Type:	instant

- Definition

Amount billed to customers under long-term contracts or programs that have been withheld because of retainage provisions in a contract.

+ References

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-Publisher FASB
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- Definition

Amount billed to customers under long-term contracts or programs that have been withheld because of retainage provisions in a contract to be collected after the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- References

No definition available.

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- References

No definition available.

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- Definition

Amount of cash restricted as to withdrawal or usage, classified as current. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
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